1. Technical Field
The present disclosure relates generally to image capture, and more particularly to digital imaging systems in which multiple self-contained camera modules are controlled, and link board hardware therefor.
2. Related Art
Image capture is fundamentally the focusing of a specific amount of light from a scene for a specific duration on to a photosensitive element of a specific sensitivity. Although having its origins in chemical-based processes using light-sensitive film, most conventional image capture systems are digital, with film being replaced with a sensor that converts photons of light into electronic signals. An optical lens focuses the light onto the sensor, with the focal length of the lens determining the width of the scene that is recorded. An adjustable aperture within the lens sets the amount of light that is passed to the sensor, while a shutter is opened for an adjustable, predetermined duration in which the sensor is exposed to the light passing through the lens. The shutter may be a mechanical device that physically blocks light from being passed to the sensor, though it may also be implemented electronically by activating the sensor only for the specified duration.
The electronic signals corresponding to the different wavelengths and intensities of light captured by the sensor are then converted to digital data via an analog-to-digital converter (ADC). The total exposure, which is defined as a combination of intensity and duration, that is needed for a proper image also depends upon the sensitivity or speed of the sensor, which can be variably set. The data is then stored on an on-board memory device such as flash memory. The foregoing operational principle is applicable to both static images as well as video, which is an extension to multiple images that are time-sequenced.
The components utilized to implement this basic image capture functionality, e.g., the lens, sensor, and controller/data processor, are well known and are available in a wide range of sizes and configurations that may be readily adapted to different platforms such as mobile communications devices, system cameras, as well as aerial vehicles to obtain footage of otherwise inaccessible locations. Depending on the needed field of view and resolution, as well as the anticipated lighting conditions of the scene to be captured, different lens and sensors may be utilized. Furthermore, the sensitivity range of imaging sensors are not limited to visual wavelengths, and there are infrared, ultraviolet, and x-ray sensors that can be used for diagnostic applications as well as for artistic effect. Although quality is constantly being improved, component size/weight and resultant image quality are oftentimes inversely related, with an emphasis towards one being a compromise with respect to the other. For example, higher resolution images are possible with larger sensors, while more compact sensors tend to be noisier. Moreover, lenses of maximum aperture and highest quality (maximum contrast and resolution, minimal aberrations across the entire diameter) are typically larger and heavier.
A typical system camera is comprised of a body incorporating the sensor and various control inputs such as the shutter button, shutter speed adjustments, and sensor sensitivity adjustments, along with one more interchangeable lenses of differing focal lengths and maximum aperture. Different lens focal lengths capture a scene aesthetically differently, so in order to provide the photographer a palette options that can be selected as desired, lenses for system cameras are offered in multiple focal lengths. Zoom lenses in which the focal length is variable may also be available. Whether fixed or variable focal length, the lenses typically include control inputs for adjusting aperture and focus, and in the case of zoom lenses, control inputs for adjusting focal length/zoom level.
Although some photographers rely on more than one body each equipped with different lenses during a photographic assignment, the components of the body, including the sensor, are not intended to be interchangeable from one shoot to the next. Further, because the photographer has immediate access to the camera body and to the lenses during operation, the hardware implementation thereof is more generalized, with an extensive variety of configuration settings and functionalities being definable and accessible via a software-implemented user interface.
With imaging systems that are incorporated into unmanned aircraft and other remotely controlled vehicles, however, there are substantial size and weight constrains due to the limited power plant and power source in typical configurations. Accordingly, the cameras are typically smaller and have more specifically defined or limited functionality that is selected for a given aerial photography/videography assignment. In one flight, the vehicle may be equipped with one sensor/lens/lens filter combination that is ideal for one subject and lighting condition (e.g., sunset landscape shots for which a faster, extreme wide angle lens with a polarizing filter is appropriate). In a different flight, the same vehicle may be equipped with a different sensor/lens/lens filter combination that is ideal for a different subject and lighting condition (e.g., daytime footage of a house for a real estate advertisement for which a conventional, standard focal length lens with minimal distortion is appropriate).
An aerial vehicle combined with an imaging system may serve a variety of duties beyond the aforementioned aerial photography, including agricultural, environmental, wildlife, and other surveys of land, inspection of power lines and other structures that are difficult to access and observe, search and rescue, and so on. These assignments may call for more than one camera, and so there is a need in the art for an imaging system in which multiple cameras can be controlled as a single unit. Furthermore, there is a need for individual camera units with such different capabilities to be readily added and subtracted to the system as dictated by particular needs without limiting flight time by carrying unneeded camera units.